Chemical Combination

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1. A student analysed two different compounds of carbon and oxygen. In the first compound, 12 g of carbon combines with 16 g of oxygen. In the second compound, 12 g of carbon combines with 32 g of oxygen. Which law of chemical combination is illustrated by the ratio of the masses of oxygen that combine with a fixed mass of carbon?

   1. A Law of definite proportions
   2. B Law of conservation of matter
   3. C Law of multiple proportions
   4. D Law of reciprocal proportions

2. In a reaction, 12 g of magnesium reacts with 16 g of oxygen to form 28 g of magnesium oxide. If 24 g of magnesium is heated in a sealed container containing 32 g of oxygen, what mass of magnesium oxide will be formed, assuming the reaction goes to completion?

   1. A 56 g
   2. B 28 g
   3. C 44 g
   4. D 60 g

3. Element X forms two oxides. In the first oxide, 1.0 g of X combines with 0.50 g of oxygen. In the second oxide, 1.0 g of X combines with 0.75 g of oxygen. If the formula of the first oxide is XO, what is the formula of the second oxide?

   1. A XO2
   2. B X2O
   3. C XO3
   4. D X2O3

4. A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Given that the relative molecular mass of the compound is 180, what is its molecular formula? (Relative atomic masses: C = 12, H = 1, O = 16)

   1. A C6H12O6
   2. B CH2O
   3. C C3H6O3
   4. D C12H24O12

5. In the reaction between aluminium and oxygen to form aluminium oxide, 27.0 g of aluminium reacts completely with oxygen. What mass of aluminium oxide is produced? (Relative atomic masses: Al = 27, O = 16)

   1. A 25.5 g
   2. B 102.0 g
   3. C 153.0 g
   4. D 51.0 g

6. A hydrocarbon, CxHy, undergoes complete combustion. If 1 mole of the hydrocarbon produces 4 moles of carbon dioxide and 5 moles of water, what is the molecular formula of the hydrocarbon?

   1. A C4H8
   2. B C2H10
   3. C C4H10
   4. D C8H5

8. In a reaction, 2.4 g of magnesium reacts completely with oxygen to form 4.0 g of magnesium oxide. What is the empirical formula of the oxide? (Relative atomic masses: Mg = 24, O = 16)

   1. A Mg2O
   2. B MgO
   3. C MgO2
   4. D Mg2O3

9. In the reaction 2Al + 3CuSO4 -> Al2(SO4)3 + 3Cu, how many moles of copper are produced when 0.5 moles of aluminium react completely with excess copper(II) sulphate?

   1. A 0.75 moles
   2. B 0.5 moles
   3. C 1.5 moles
   4. D 0.33 moles

10. A student burns 2.8 g of iron in excess oxygen to form iron(III) oxide (Fe2O3). What is the mass of iron(III) oxide produced? (Relative atomic masses: Fe = 56, O = 16)

    1. A 2.0 g
    2. B 8.0 g
    3. C 5.6 g
    4. D 4.0 g

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